The present invention relates to a telephone keyset system; that is, a telephone system having keysets with a number of dial, line and function keys for home or office use--which may contain one or more of a number of telephone "features" and "functions"--as well as ancillary telephone apparatus such as a busy lamp field console, a telephone accessory unit, a printer, etc.
As is well known, the standard telephone comprises an acoustic/electrical transducer or microphone, an electrical/acoustic transducer or earphone, a hook switch, a dialing mechanism and a bell or buzzer. The structure required to include these features need be no larger than a telephone handset. In fact, telephone instruments are known in which the handset itself is comprised of two pieces which are folded over when in the rest or "on-hook" position, and which fold out into a convenient handset size when lifted off a flat surface into the "off-hook" position for use in communicating.
As the cost of electronic equipment is currently falling, many hardware "features" have been and are being added to this otherwise rather prosaic device. Some typical features which a telephone instrument may include are: p1 (1) a plurality of "line" keys which, when depressed, connect the telephone to different lines;
(2) a plurality of "function" keys which, when depressed, initiate one or more of a number of telephone functions; PA1 (3) a display which images a number of alphanumeric characters; PA1 (4) a microphone for "handsfree" speaking; PA1 (5) a speaker for "handsfree" listening; PA1 (6) an external unit jack for connecting the telephone to a printer, a digital data interface unit, a magnetic recorder for taking messages, a console containing additional line and function keys and/or another unit such as an external computer, CRT display and the like; and PA1 (7) a small computer which may be utilized by the customer as a programmable element as well as to control the instrument.
Experience has shown that more and more "functions" or modes of operation have also been, and will be added to the telephone instrument to make it a most convenient and versatile piece of equipment. Not only will the telephone in the future serve each user as an instrument of voice and data communications, it will also serve other telecommunication functions such as providing music, external paging, message recording and/or dictation access; room and building security against unauthorized access and/or fire; and room and building energy control such as lighting, heat and air conditioning. As mentioned above, the telephone instrument may also serve as a small, handy computer which can operate off-line or in direct communication with another computer at another location.
When designing a telephone "keyset"--that is, a telephone instrument with a number of keys for dialing and for other functional purposes--it is desirable to take into consideration and provide for the possibility of implementing the various features and functions such as those enumerated above. More particularly, it is desirable to develop an economical and efficient telephone "package" which is not significantly larger than presently existing telephones and which may be implemented inexpensively as a "modular" telephone instrument which can be readily tailored to meet the needs of each customer. Such a modular structure would facilitate the creation of a "family" of telephones, telephone consoles and other ancillary equipment, from option-laden instruments having all the available features and functions to a basic telephone instrument constructed at minimum cost.
Simply stated, it is desired to develop a telephone keyset system structure which may be implemented inexpensively with numerous optional features and functions, or implemented, as desired, without these features and functions at a cost which is not significantly greater than the present cost of telephone instruments.